Graded particle-size retention filter medium for cell-type filter unit

Abstract

A cell-type filter unit having two or more filter media layers and/or zones, at least one of the layers/zones having a different particle retention capability disposed on each side of a non-filtering separator element. The filter media are preferably positioned such that each succeedingly distal filter layer or zone from the separator has a decreased particle retention capability than each proceeding filter layer or zone. The filter media layer most proximal to the separator element may be separated from the separator by a support material for supporting such filter media element and preventing collapsing of the media into any separator conduit.

What is claimed is:  
     
         1 . A cell-type filter unit comprising: an upper composite filter medium element, a lower composite filter medium element; a non-filtering separator element disposed between said upper composite filter medium element and said lower composite filter medium element; and a sealing edge operatively connecting said lower and upper filter medium element along their edges; wherein said lower and upper composite filter medium elements are comprised of at least two zones of filter material, each zone having a different PRC, such that at least one zone of each medium is disposed proximal to said separator element and at least one zone of each medium is disposed distal to said separator element.  
     
     
         2 . The cell-type filter unit of  claim 1  wherein the zone disposed most proximal to said separator element has a greater standardized-PRC than the zone disposed most distal to said separator element.  
     
     
         3 . The cell-type filter unit of  claim 1  wherein the zone disposed most proximal to said separator element has a greater relative-PRC than the zone disposed most distal to said separator element.  
     
     
         4 . The cell-type filter unit of  claim 1  wherein the zone disposed most proximal to said separator element has a lower tandardized-PRC than the zone disposed most distal to said separator element.  
     
     
         5 . The cell-type filter unit of  claim 1  wherein the zone disposed most proximal to said separator element has a lower relative-PRC than the zone disposed most distal to said separator element.  
     
     
         6 . The cell-type filter unit of  claim 1  wherein the zone disposed most proximal to said separator element has a lower standaradized-PRC than the zone disposed most distal to said separator element.  
     
     
         7 . The cell-type filter unit of  claim 1  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a larger relative-PRC.  
     
     
         8 . The cell-type filter unit of  claim 1  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a larger standardized-PRC.  
     
     
         9 . The cell-type filter unit of  claim 1  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a smaller relative-PRC.  
     
     
         10 . The cell-type filter unit of  claim 1  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a smaller standardized-PRC.  
     
     
         11 . The cell-type filter unit of  claim 1  wherein the zones of filter material are integral with one another.  
     
     
         12 . The cell-type filter unit of  claim 1  wherein the zones of filter material are separate layers operatively connected to one another.  
     
     
         13 . The cell-type filter unit of  claim 4  wherein the CHC per unit area of the composite filter medium is greater than the CHC per unit area of the zone most distal from said separator when such zone is extrapolated to the depth of the composite medium.  
     
     
         14 . The cell-type filter unit of  claim 5  wherein the CHC per unit area of the composite filter medium is greater than the CHC per unit area of the zone most distal from said separator when such layer is extrapolated to the depth of the composite medium.  
     
     
         15 . The cell-type filter unit of  claim 1  wherein each succeeding layer towards said separator element from the zone disposed most distal from said separator element, is capable of retaining particles of smaller size than the preceding layer.  
     
     
         16 . The cell-type filter unit of  claim 1  wherein at least one filter medium zone comprises melt-blown material.  
     
     
         17 . The cell-type filter unit of  claim 15  wherein the melt-blown material is selected from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         18 . The cell-type filter unit of  claim 1  wherein at least one filter medium layer comprises microporous membrane.  
     
     
         19 . The cell-type filter unit of  claim 18  wherein said microporous membrane is nylon.  
     
     
         20 . The cell-type filter unit of  claim 18  wherein the microporous membrane is a reinforced, three-zone microporous membrane.  
     
     
         21 . The cell-type filter unit of  claim 20  wherein each of the zones of the reinforced, three zone microporous membrane has a different PRC as compared to the other zones.  
     
     
         22 . The cell-type filter unit of  claim 1  further comprising: a support zone operatively disposed proximal to said non-filtering separator element for supporting the composite filter medium most proximal to said non-filtering separator element.  
     
     
         23 . The cell-type filter unit of  claim 22  wherein the support zone comprises spun bound non-woven material.  
     
     
         24 . The cell-type filter unit of  claim 23  wherein the non-woven material is selected from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         25 . The cell-type filter unit of  claim 22  wherein the support zone comprises plastic netting.  
     
     
         26 . The cell-type filter unit of  claim 25  wherein the plastic netting is fabricated from a material from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         27 . The cell-type filter unit of  claim 1  wherein the difference between the PRC of the zones of each composite filter medium is greater than about 10%.  
     
     
         28 . The cell-type filter unit of  claim 1  wherein the difference between the PRC of the zones of each composite filter medium is greater than about 25%.  
     
     
         29 . The cell-type filter unit of  claim 1  wherein the difference between the PRC of the zones of each composite filter medium is greater than about 50%.  
     
     
         30 . A cell-type filter unit comprising: an upper filter medium element having top, bottom and edge surfaces; a lower filter medium element having top, bottom and edge surfaces; a non-filtering separator element disposed between said bottom surface of said upper filter medium element and said top surface of said lower filter medium element in such a manner to be anterior to said lower filter medium element and posterior to said upper filter medium; and a sealing edge operatively connecting said lower and upper filter medium element along their edges, wherein said lower and upper filter medium have a graded PRC from said top surface to said bottom surface of said filter media such that when a suspension containing a diverse particle-size distribution flows from said top surface to said bottom surface more small particles are retained as the depth from the top surface increases.  
     
     
         31 . The cell-type filter unit of  claim 30  wherein the standardized-PRC is graded.  
     
     
         32 . The cell-type filter unit of  claim 30  wherein the relative-PRC is graded.  
     
     
         33 . The cell-type filter unit of  claim 30  wherein at least one filter medium comprises melt-blown material.  
     
     
         34 . The cell-type filter unit of  claim 33  wherein the melt-blown material is selected from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         35 . The cell-type filter unit of  claim 30  wherein at least one filter medium comprises a microporous membrane.  
     
     
         36 . The cell-type filter unit of  claim 35  wherein said microporous membrane is nylon.  
     
     
         37 . The cell-type filter unit of  claim 35  wherein the microporous membrane is a reinforced, three zone microporous membrane.  
     
     
         38 . The cell-type filter unit of  claim 37  wherein each of the zones of the re-inforced, three zone microporous membrane has a different PRC as compared to the other zones.  
     
     
         39 . The cell-type filter unit of  claim 30  further comprising: a support layer disposed proximal to said non-filtering separator element for supporting the filter medium most proximal to said non-filtering separator element.  
     
     
         40 . The cell-type filter unit of  claim 39  wherein the support layer comprises spun bound non-woven material.  
     
     
         41 . The cell-type filter unit of  claim 40  wherein the support layer comprises plastic netting.  
     
     
         42 . A cell-type filter unit comprising: an upper filter medium element having top, bottom and edge surfaces; a lower filter medium element having top, bottom and edge surfaces; a non-filtering separator element disposed between said bottom surface of said upper filter medium element and said top surface of said lower filter medium element in such a manner to be anterior to said lower filter medium element and posterior to said upper filter medium; and a sealing edge operatively connecting said lower and upper filter medium element along their edges, wherein said lower and upper filter medium have a graded pore-size from said top surface to said bottom surface of said filter media such that a larger number of relatively larger pore sizes are found toward the top surface, whereas a larger number of relatively smaller size pore sizes are found toward said bottom surface of the filter media, and pore size distribution varies as a function of depth into the filter medium.  
     
     
         43 . The cell-type filter unit of  claim 42  wherein at least one filter medium comprises melt-blown material.  
     
     
         44 . The cell-type filter unit of  claim 43  wherein the melt-blown material is selected from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         45 . The cell-type filter unit of  claim 42  wherein at least one filter medium comprises a microporous membrane.  
     
     
         46 . The cell-type filter unit of  claim 45  wherein said microporous membrane is nylon.  
     
     
         47 . The cell-type filter unit of  claim 45  wherein the microporous membrane is a reinforced, three-zone microporous membrane.  
     
     
         48 . The cell-type filter unit of  claim 47  wherein each of the zones of the re-inforced, three zone microporous membrane has a different PRC as compared to the other zones.  
     
     
         49 . The cell-type filter unit of  claim 40  further comprising: a support layer disposed proximal to said non-filtering separator element for supporting the filter medium most proximal to said non-filtering separator element.  
     
     
         50 . The cell-type filter unit of  claim 49  wherein the support layer comprises spun bound non-woven material.  
     
     
         51 . The cell-type filter unit of  claim 50  wherein the support layer comprises plastic netting.  
     
     
         52 . A cell-type filter cartridge comprising: a plurality of cell-type filter units, each cell-type filter unit having an upper filter medium element surrounding a central void; a lower filter medium element surrounding a central void; a non-filtering separator element surrounding a central void disposed between said upper filter medium element and said lower filter medium element; and a sealing edge sealing edge operatively connecting said lower and upper filter medium elements along their edges, mounted generally parallel to and spaced from one another such that the a central continuous bore is formed there-between, wherein the filter media of the cell-type filter units are each comprised of at least two zones of filter material each zone having a different PRC.  
     
     
         53 . The cell-type filter unit of  claim 52  wherein the zone disposed most proximal to said separator element has a greater standardized-PRC than the zone disposed most distal to said separator element.  
     
     
         54 . The cell-type filter unit of  claim 52  wherein the zone disposed most proximal to said separator element has a greater relative-PRC than the zone disposed most distal to said separator element.  
     
     
         55 . The cell-type filter unit of  claim 52  wherein the zone disposed most proximal to said separator element has a greater standardized-PRC than the zone disposed most distal to said separator element.  
     
     
         56 . The cell-type filter unit of  claim 52  wherein the zone disposed most proximal to said separator element has a lower relative-PRC than the zone disposed most distal to said separator element.  
     
     
         57 . The cell-type filter unit of  claim 52  wherein the zone disposed most proximal to said separator element has a lower standardized-PRC than the zone disposed most distal to said separator element.  
     
     
         58 . The cell-type filter unit of  claim 52  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a larger relative-PRC.  
     
     
         59 . The cell-type filter unit of  claim 52  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a larger standardized-PRC.  
     
     
         60 . The cell-type filter unit of  claim 52  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a smaller relative-PRC.  
     
     
         61 . The cell-type filter unit of  claim 52  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element has a smaller standardized-PRC.  
     
     
         62 . The cell-type filter unit of  claim 52  wherein the zones of filter material are integral with one another.  
     
     
         63 . The cell-type filter unit of  claim 52  wherein the zones of filter material are separate layers operatively connected to one another.  
     
     
         64 . The cell-type filter unit of  claim 62  wherein the CHC per unit area of the composite filter medium is greater than the CHC per unit area of the zone most distal from said separator when such zone is extrapolated to the depth of the composite medium.  
     
     
         65 . The cell-type filter unit of  claim 63  wherein the CHC per unit area of the composite filter medium is greater than the CHC per unit area of the zone most distal from said separator when such layer is extrapolated to the depth of the composite medium.  
     
     
         66 . The cell-type filter unit of  claim 52  wherein each succeeding zone towards said separator element from the zone disposed most distal from said separator element, is capable of retaining particles of smaller size than the preceding zone.  
     
     
         67 . The cell-type filter unit of  claim 52  wherein at least one filter medium zone comprises melt-blown material.  
     
     
         68 . The cell-type filter unit of  claim 67  wherein the melt-blown material is selected from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         69 . The cell-type filter unit of  claim 52  wherein at least one filter medium layer comprises microporous membrane.  
     
     
         70 . The cell-type filter unit of  claim 69  wherein said microporous membrane is nylon.  
     
     
         71 . The cell-type filter unit of  claim 69  wherein the microporous membrane is a reinforced, three-zone microporous membrane.  
     
     
         72 . The cell-type filter unit of  claim 71  wherein each of the zones of the reinforced, three zone microporous membrane has a different PRC as compared to the other zones.  
     
     
         73 . The cell-type filter unit of  claim 52  further comprising: a support zone operatively disposed proximal to said non-filtering separator element for supporting the composite filter medium most proximal to said non-filtering separator element.  
     
     
         74 . The cell-type filter unit of  claim 73  wherein the support zone comprises spun bound non-woven material.  
     
     
         75 . The cell-type filter unit of  claim 74  wherein the non-woven material is selected from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         76 . The cell-type filter unit of  claim 73  wherein the support zone comprises plastic netting.  
     
     
         77 . The cell-type filter unit of  claim 76  wherein the plastic netting is fabricated from a material from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         78 . The cell-type filter unit of  claim 52  wherein the difference between the PRC of the zones of each composite filter medium is greater than about 10%.  
     
     
         79 . The cell-type filter unit of  claim 52  wherein the difference between the PRC of the zones of each composite filter medium is greater than about 25%.  
     
     
         80 . The cell-type filter unit of  claim 52  wherein the difference between the PRC of the zones of each composite filter medium is greater than about 50%.  
     
     
         81 . A multi-zone filtration media cell-type filter unit prepared by a process comprising the steps of: providing a first set of filter media, each filter medium having about the same dimension, shape and PRC; providing a second set of filter media, each filter medium having about the same dimension and shape as, and having a PRC different than that of said first set of filter media; providing a separator element of about the same shape and dimension as said filter medium of said first and second set of filter media, said separator element significantly lacking filtering capacity; operatively assembling the first set of filter media, the second set of filter media and the separator element to form a composite structure; and operatively joining the filter media of said composite structure along the edges of the filter media to seal the outer edge thereof.  
     
     
         82 . The cell-type filter unit of  claim 81  wherein the difference between the PRC between the first set and second set of filter media is greater than about 10%.  
     
     
         83 . The cell-type filter unit of  claim 81  wherein the difference between the PRC between the first set and second set of filter media is greater than about 25%.  
     
     
         84 . The cell-type filter unit of  claim 81  wherein the difference between the PRC between the first set and second set of filter media is greater than about 50%.  
     
     
         85 . A multi-zone filtration media cell-type filter unit prepared by a process comprising the steps of: providing a first filter medium zone having a particular PRC; overfelting the first filter medium zone with a second filter medium zone of different PRC, such that the first filter medium zone is substantially entirely covered on one surface thereof; providing a substantially non-filtering separator element of such shape and dimension to extend the surface of said first filter medium which opposes the overfelted surface; operatively joining said overfelted filter medium with said separator element along the edges of the overfelted filter media to seal the outer edge thereof.  
     
     
         86 . The cell-type filter unit of  claim 85  wherein the difference between the PRC of the first filter medium zone as compared to the second filter medium zone is greater than about 10%.  
     
     
         87 . The cell-type filter unit of  claim 85  wherein the difference between the PRC of the first filter medium zone as compared to the second filter medium zone is greater than about 25%.  
     
     
         88 . The cell-type filter unit of  claim 85  wherein the difference between the PRC of the first filter medium zone as compared to the second filter medium zone is greater than about 50%.  
     
     
         89 . A cell-type filter unit comprising: a first upper filter medium zone having top, bottom and edge surfaces; a second upper filter medium zone having top, bottom and edge surfaces, and disposed with respect to said first upper filter medium zone such that the top surface of said second upper filter medium zone is in intimate contact with the bottom surface of said first upper filter medium zone; a first lower filter medium zone having top, bottom and edge surfaces, a second lower filter medium zone having top, bottom and edge surfaces, and disposed with respect to said first lower filter medium zone such that the top surface of said second lower filter medium zone is in intimate contact with the bottom surface of said first lower filter medium zone; a substantially non-filtering separator element disposed between said upper filter media zones and lower filter media zones in such a manner to be posteriorally proximal to said bottom surface of said second lower filter medium zone and anteriorally proximal to said bottom surface of said second upper filter medium zone; and a sealing edge operatively connecting said upper filter media zones and said lower filter media zones along their edges, wherein said upper and lower filter media zones have a graded PRC from said top surface of said first filter medium zone to said bottom surface of said second filter medium zone.  
     
     
         90 . The cell-type filter unit of  claim 89  wherein the first upper filter medium zone, second upper filter medium zone, first lower filter medium zone and second lower filter medium zone have the same composition and fabrication, and substantially the same charge.  
     
     
         91 . The cell-type filter unit of  claim 90  wherein each zone differs as to average pore size.  
     
     
         92 . The cell-type filter unit of  claim 89  wherein each zone has a graded PRC.  
     
     
         93 . The cell-type filter unit of  claim 92  wherein the standardized-PRC is graded.  
     
     
         94 . The cell-type filter unit of  claim 92  where the relative-PRC is graded.  
     
     
         95 . The cell-type filter unit of  claim 89  wherein at least one filter medium zone comprises melt-blown material.  
     
     
         96 . The cell-type filter unit of  claim 95  wherein the melt-blown material is selected from the group consisting of: polypropylene, polyethylene, polyester and nylon.  
     
     
         97 . The cell-type filter unit of  claim 89  wherein at least one filter medium zone comprises a microporous membrane.  
     
     
         98 . The cell-type filter unit of  claim 97  wherein said microporous membrane is nylon.  
     
     
         99 . The cell-type filter unit of  claim 97  wherein the microporous membrane is a re-inforced, three-zone microporous membrane.  
     
     
         100 . The cell-type filter unit of  claim 99  wherein each zone of the reinforced, three zone microporous membrane has a different PRC as compared to the other zones.  
     
     
         101 . The cell-type filter unit of  claim 89  further comprising: a support layer, disposed proximal to said substantially non-filtering separator element, for supporting the filter medium most proximal to said substantially non-filtering separator element.  
     
     
         102 . The cell-type filter unit of claim  101  wherein the support layer comprises spun bound non-woven material.  
     
     
         103 . The cell-type filter unit of claim  101  wherein the support layer comprises plastic netting.  
     
     
         104 . A cell-type filter unit comprising: an upper composite filter medium element, a lower composite filter medium element; a non-filtering separator element disposed between said upper composite filter medium element and said lower composite filter medium element; and a sealing edge operatively connecting said lower and upper filter medium element along their edges; wherein said lower and upper composite filter medium elements consist of at least two zones of filter material, each zone comprising about 30 to about 50 percent cellulose and about 50 to about 70 percent filter aid, and, each zone having an airflow pressure drop across the zone which differs by more than about 10 percent from the other zones, wherein each succeeding zone of medium disposed from the separator element has a lower air pressure drop across the zone than any preceding zone which is more proximal to the separator element.  
     
     
         105 . The cell-type filter unit of claim  104  wherein each zone has an airflow pressure drop across the zone which differs by more than about 25 percent from the other zones and wherein each succeeding zone of medium disposed from the separator element has a lower air pressure drop across the zone than any preceding zone which is more proximal to the separator element.  
     
     
         106 . The cell-type filter unit of claim  104  wherein each zone has an average pore size differing by more than about 10 percent from the other zones and wherein each succeeding zone of medium disposed from the separator element has a larger average pore size than any preceding zone which is more proximal to the separator element.  
     
     
         107 . The cell-type filter unit of claim  104  wherein each zone has an average pore size differing by more than about 25 percent from the other zones, and wherein each succeeding zone of medium disposed from the separator element has a larger average pore size than any preceding zone which is more proximal to the separator element.